'88 Mr. W, Evans on the Periods 



long period^ six weeks or thereabout. The great difference 

 between the Cormorant's period and that of the Gannet is 

 worthy of notice in connection with the fact that the former 

 lays from 3 to 5 eggs^ while the latter only lays 1 . 



The statements regarding the Herodiones are very con- 

 flicting, but I think we may hold their periods of incubation 

 to be much on a par with those of the Anseres. Taking the 

 Common Heron as a typical example of the Order, we have 

 a period apparently identical with that of the Wild Duck, 

 namely, 25 to 26 days, and their eggs may be said to be 

 much about the same size. According to Naumann the 

 Little Bittern takes from 16 to 17 days only, and we have 

 the Stork set down at 30 days by Macgillivray. 



In the case of the Anseres we are on much surer ground, 

 the duration of incubation passing very naturally from 3 

 weeks in the smaller Ducks to about 30 days in the typical 

 Geese, and on to 35 to 40 days in the Swans. A very com- 

 mon opinion in regard to the Ducks is that they all sit 28 

 days ; but I think my experiments prove that the eggs of the 

 Common Wild Duck hatch in from 25 to 26 days, and those 

 of the Teal in from 21 to 22. The Flamingos are probably 

 very similar to the Geese in this respect. 



Judging by the time our own Common Pigeons — wild and 

 tame — take to hatch (15 to 17 days), I had come to look on 

 the Columbce as a short-period group, and consequently was 

 much surprised to find that the Nicobar and the Crowned 

 Pigeons in the Zoological Society's Gardens took no less than 

 28 days to bring out their young. 



It is gratifying to be able to include in my list two species 

 of the limited Order Pterocles, namely the Pin-tailed and the 

 Pallas's Sand-Grouse. The periods given, 25 and 28 days 

 respectively, do not bear out a statement I have somewhere 

 seen, to the effect that the duration of incubation in the case 

 of Syrrhaptes paradoxus is unusually short. 



The Gallina present less variation than we might expect 

 when their great diversity of size is considered. The Quails 

 require about 3 weeks, and a week more suffices for a Turkey. 

 It seems strange that the period of incubation in the case 



